An estimated 8,000 transplants of marrow, peripheral blood stem cells and umbilical cord blood stem cells took place in 1996. Additional indications for transplantation of hematopoietic stem cells are continually being reported, steadily increasing the number and frequency of transplants. The complexity of cell processing for transplantation also continues to grow and evolve rapidly, often resulting in longer processing times and necessitating transportation of cells to centers capable of performing more sophisticated cell processing procedures.
Hematopoietic transplantation may involve a donor and recipient treated at different institutions, e.g., allogenic transplantation. For autologous transplants, bone marrow is occasionally sent to a larger hospital for specialized treatment, such as the purging of tumor cells. Occasionally, cells to be transplanted are collected at one hospital, then transported to the transplant institution where the cells undergo processing and transplant. Due to geographic separation between donor and recipient, cells may be in transport for extended periods of time e.g., 36 hours, and sometimes much longer between the cell harvest and arrival at the processing laboratory as many donor programs match donor and recipients in different countries.
Following transport, cells can arrive at a processing laboratory at virtually any hour of the day or night, often with extensive processing still to be performed. The processing laboratory faces two alternatives: (1) to store the cells until daytime staff are available, or (2) to process the cells for transplantation immediately upon receipt. The latter requires 24-hour staffing for the processing laboratory and is clearly not possible at most institutions. The former alternative presents the problem of how to store the cells, in which bags, at what temperature and in which medium or solution. Clinical laboratories in general are neither staffed nor equipped to solve this problem to the satisfaction of transplant clinicians.
Since the publication in 1970 of the Thomas and Storb article on human marrow grafting, tissue culture medium has been used for the collection of transplantable hematopoietic stem cells. (Thomas et al., Blood 36:507-515 (1970)). Presently, cells are transported and stored in solutions composed of tissue culture medium. Several different formulations, most commonly .alpha.-MEM, IMDM, and RPMI-1640 are currently in use, although two other media, X-VIVO-10 and AIM-V, are also used less frequently (Areman, et al. Bone Marrow Transplant 6:203-209 (1990); Areman et al., Transfusion 31:724-730 (1991)).
Media currently utilized are designated for in vitro use only and contain combinations of inorganic salts, amino acids, vitamins, sugars, dyes, e.g., phenol red and other constituents not available in U.S.P. grade. These solutions employ a phosphate-based buffering system designed for use in the 5% CO.sub.2 atmosphere of a cell culture incubator. Such a buffering system is, however, ineffective at atmospheric CO.sub.2 concentrations. Cells stored and transported in these solutions are essentially without environmental pH control. Additionally, none of the media have ever been rigorously tested to determine whether one medium is superior or inferior to the others.
Because of the increasingly widespread use of bone marrow and peripheral blood progenitor cells in the treatment of malignancies and hematopoietic disorders, accrediting and regulatory agencies are developing and issuing standards and guidelines for the preparation of components for transplantation (Phillips et al., Biol. Of Blood and Marrow Transpln. 1:54-55 (1995); Standards for hematopoietic progenitor cell collection, processing and transplantation, Foundation for the Accreditation of Hematopoietic Cell Therapy ("FAHCT") 1st edn. (1996)). None of the tissue culture media used in marrow collection have been licensed by the United States Food and Drug Administration for in vivo human use. Other non-licensed agents such as dimethylsulfoxide ("DMSO") and Ficoll-hypaque are also used in the processing and preservation of stem cells and other hematopoietic cells but at this time there are no comparable approved substances with which to replace them.
There is a need for a medium for short-term storage of stem cells, nucleated cells, e.g., mononuclear cells, and other hematopoietic cells prior to, during and after processing or that will permit shipment of cells from a processing center to a transplant center. Thus, an infusible-grade storage medium capable of maintaining cell viability and functional capability would be of great value.